Manatee Pocket

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Silt build-up - worsened by recent hurricanes - has reduced the Pocket's depth to 4-5 feet in some areas, making it is difficult or impossible for large yachts to reach waterfront business. The waterway also has a generally degraded habit, with silt covering most of its bottom. Concerned citizens have asked the Martin County Board of County Commissioners to sponsor dredging a channel through the Pocket to help alleviate these issues.

Importance
The importance of maintaining the commercial, recreational and navigable viability of the Manatee Pocket has been recognized by the Martin County Board of County Commissioners, who called it crucial to the county. The Commission agreed to begin researching the costs, permitting requirements and feasibility of creating a channel through the harbor.

Solution
As a first step, the County retained Tetra Tech EC, a global engineering and environmental services firm, to design a navigable waterway. Priorities include removing detrimental much, improving water quality and environment for marine life, and increasing the size/draft of vessels that can access the Pocket. The creation of this deeper navigation channel will also benefit manatee protection.

Challenges
Detailed physical and environmental surveys are required to determine accurate depths throughout the Pocket and the appropriate dredging method for the project. The channel must be designed to minimize impacts to environmental resources within the Pocket. Finally, as with most waterway access may prove to be a challenge.

The Manatee Pocket dredging project requires a state permit from the Florida Department of Environmental Protection, and a federal permit from the U.S. Army Corps of Engineers (both permit applications were submitted in January 2007). There are many environmental issues to address during this process. It is estimated that permitting will take 12 months to complete.

The proposed design channel of approximately 100 feet would be optimal to achieving the desired depth while reducing maintenance requirements. The wider channel will allow slumping of side slopes while maintaining the desired depth in the center of the channel. The volume estimate for a 100-foot-wide, 10-foot-deep channel through Manatee Pocket is 230,000 cubic yards.

Funding
Staff was authorized to proceed with this project at a Board of County Commissioners meeting on January 24, 2006. Phase I engineering costs, which would bring the project design to 30% completion, are estimated to be $175,000. Permitting and final design costs are estimated at $300,000, with construction costs ranging from $8 to $12 million. The range of the construction estimate depends on the construction and handling methods selected, as well as permit conditions imposed by the agencies.

Funding for the Manatee Pocket dredging project could come from a number of sources, including private contributions, assessments, special state appropriations, ad valorem taxes and grants. Examples of grant programs that pertain to this type of project are Florida Inland Navigation District (FIND) Waterway Assistance Program and the St. Lucie River Issues Team Grant. County engineering staff is investigating additional grant programs that focus on marine habitat restoration.